Magnetic materials and permanent magnet materials are one of the important electric and electronic materials applied in an extensive range from various electrical appliances for domestic use to peripheral terminal devices of large-scaled computers. In view of recent needs for miniaturization and high efficiency of electric and electronic equipments, there has been an increasing demand for upgrading of permanent magnet materials and generally magnetic materials.
The permanent magnet materials developed yet include alnico, hard ferrite and samarium-cobalt (SmCo) base materials which are well-known and used in the art. Among these, alnico has a high residual magnetic flux density (hereinafter referred to Br) but a low coercive force (hereinafter referred to Hc), whereas hard ferrite has high Hc but low Br.
Advance in electronics has caused high integration and miniaturization of electric components. However, the magnetic circuits incorporated therein with alnico or hard ferrite increase inevitably in weight and volume, compared with other components. On the contrary, the SmCo base magnets meet a demand for miniaturization and high efficiency of electric circuits due to their high Br and Hc. However, samarium is rare natural resource, while cobalt should be included 50-60 wt % therein, and is also distributed at limited areas so that its supply is unstable.
Thus, it is desired to develop novel permanent magnet materials free from these drawbacks.
If it could be possible to use, as the main component for the rare earth elements light rare earth elements that occur abundantly in ores without employing much cobalt, the rare earth magnets could be used abundantly and with less expense in a wider range. In an effort made to obtain such permanent magnet materials, R-Fe.sub.2 base compounds, wherein R is at least one of rare earth metals, have been investigated. A. E. Clark has discovered that sputtered amorphous TbFe.sub.2 has an energy product of 29.5 MGOe at 4.2.degree. K., and shows a coercive force Hc=3.4 kOe and a maximum energy product (BH)max=7 MGOe at room temperature upon heat-treatment at 300.degree.-500.degree. C. Reportedly, similar investigations on SmFe.sub.2 indicated that 9.2 MGOe was reached at 77.degree. K. However, these materials are all obtained by sputtering in the form of thin films that cannot be generally used as magnets, e.g., speakers or motors. It has further been reported that melt-quenched ribbons of PrFe base alloys show a coercive force Hc of as high as 2.8 kOe.
In addition, Koon et al discovered that, with melt-quenched amorphous ribbons of (Fe.sub.0.82 B.sub.0.18).sub.0.9 Tb.sub.0.05 La.sub.0.05, Hc of 9 kOe was reached upon annealing at 627.degree. C. (Br=5 kG). However, (BH)max is then low due to the unsatisfactory loop squareness of magnetization curves (N. C. Koon et al, Appl. Phys. Lett. 39 (10), 1981, pp. 840-842).
Moreover, L. Kabacoff et al reported that among melt-quenched ribbons of (Fe.sub.0.8 B.sub.0.2).sub.1-x Pr.sub.x (x=0-0.03 atomic ratio), certain ones of the Fe-Pr binary system show Hc on the kilo oersted order at room temperature.
These melt-quenched ribbons or sputtered thin films are not any practical permanent magnets (bodies) that can be used as such. It would be practically impossible to obtain practical permanent magnets from these ribbons or thin films.
That is to say, no bulk permanent magnet bodies of any desired shape and size are obtainable from the conventional Fe-B-R base melt-quenched ribbons or R-Fe base sputtered thin films. Due to the unsatisfactory loop squareness (or rectangularity) of the demagnetization curves, the Fe-B-R base ribbons heretofore reported are not taken as the practical permanent magnet materials comparable with the conventional, ordinary magnets. Since both the sputtered thin films and the melt-quenched ribbons are magnetically isotropic by nature, it is indeed almost impossible to obtain therefrom magnetically anisotropic (hereinbelow referred to "anisotropic") permanent magnets for the practical purpose comparable to the conventional hard ferrite or SmCo magnets.